Posted
by
timothy
on Monday July 21, 2008 @12:36AM
from the you'll-need-thicker-gloves dept.

phantomflanflinger writes "The Cern Laboratory, home of the Large Hadron Collider, is fast becoming one of the coolest places in the Universe. According to news.bbc.co.uk, the Large Hadron Collider is entering the final stages of being lowered to a temperature of 1.9 Kelvin (-271C; -456F) — colder than deep space. The LHC aims to re-create the conditions just after the Big Bang and continue the search for the Higgs boson."

The ever-elusive Higgs Bosom can't be directly observed (because it's like staring into the sun) therefore it must be indirectly observed -- in this case, by lowering the ambient temperature in the observational environment and watching for the most common secondary sign of it's presence, a phenomenon which researchers have fondly nicknamed the "sweater-puppy effect".

I find it ironic or at least counter-intuitive that it's necessary to create one of the coldest spaces to look for particles that flourished when things were at their hottest. It makes sense once explained, but I doubt Joe Sixpack would stick around long enough to hear it, let alone grasp it. They just think this thing is going to make a black hole that eats the planet.

It is not that impressive at all. If you read the article, they are cooling the superconducting magnets with liquid helium. (Nearly?) every university chemistry department will have an NMR spectrometer with a superconducting magnet doing at the same temperature, and many will have a SQUID going colder. So although it is *one* of the coldest places on earth, it is a fairly routine temperature.

It makes sense once explained, but I doubt Joe Sixpack would stick around long enough to hear it, let alone grasp it.

Not just Joe Sixpack, but anybody who doesn't care much about the experiment at this point. It's like listening to Joe Sixpack's plans for a rock climbing trip... tell me all the details after something interesting has happened.

If the Large Hadron Collider begins to smoke, get away immediately. Seek shelter and cover head.

The Large Hadron Collider may stick to certain types of skin.

When not in use, the Large Hadron Collider should be returned to its special container and kept under refrigeration. Failure to do so relieves the makers of the Large Hadron Collider, the scientific community, and its parent company, the military-industrial complex, of any and all liability.

Ingredients of the Large Hadron Collider include an unknown glowing green substance which fell to Earth, presumably from outer space.

The Large Hadron Collider has been shipped to our troops in Saudi Arabia and is being dropped by our warplanes on Iraq.

If the magnets are superconducting, why would they need a good thermal conductor? It's not as if superconductors generate any heat in operation.

And are they really going to push the magnetic fields up to the point where they truly need to cool high-temp superconductors down to the edge of absolute zero? TFA says they're using enormous currents, but doesn't this leave an awful small margin?

HTC technology is not available yet for applications like this. They are using conventional Sn3Ti (and NbTi to some extent) superconductors.
I'm not sure how the Wikipedia quote is relevant here. Although the wires in LHC are made of LTS materials, the materials still are type II superconductors.
The main reason to have large cooling capacity is a phenomenon called "quenching". The wires in the coils are actually made of really thin filaments of superconducting material inside a copper matrix. These filaments can (and do) go out of superconducting state because of a local problem, and at this small point there's naturally high ohmic heating. If the system can't respond quickly enough to lower the local temperature so that the superconducting state is restored, this point of normal state will start to spread at a high speed, causing more heating and boiling off the coolant quite expensively. So this is the reason why you need large cooling capacity and thermal conductivity.

The superconducting cables may still have some temperature fluctuation which takes a small part out of its superconducting state. When this happens all that current suddenly becomes ohmic and the cable is potentially destroyed (quench). They design in regular cable strands (copper usually) which can carry this current for a split second until circuits turn off the entire cable before it is destroyed. Otherwise you're hoping your cable remains perfectly cool, and if it fails you have to replace millions of d

Spontaneous fluctations in magnitude of more than several degrees are HIGHLY improbable (as in "unlikely to happen during the Universe's lifetime").

However, different equipment failures can happen. That's why cables are cooled slightly below the boiling point of helium. Which itself is well below the critical temperature for Nb-Ti and Nb superconductors.

In a type II superconductor when in its mixed phase state it has lines of superconducting and lines of normal areas called flux. In a field there is a force on the flux lines and they tend to move creating heat. All this happens even though it has zero resistance.

Caveat emptor is not english either. Caveat is latin for warning. See Wikipedia [wikipedia.org]. So when someone says "with some caveats in strong magnetic fields" it is technically incorrect. Since "with some warnings in strong magnetic fields" isn't what he intended to say. However, caveat can be used correctly on its own. E.g. He entered the cave dispite his companion's caveat.

No. One more time: there's NO resistance. In one experiment, for example, there were no measurable current decrease in a magnet after 20 years.

Low-TC superconductors are preferable because they have much higher critical current. Superconductors lose their superconductivity when a high enough magnetic field is applied. This magnetic field can be external or generated by the current passing through the superconductor itself.

Oh, and 1.9K temperature is used because it has a margin of safety for liquid helium (which has 4K boiling point).

Its Schwarzchild radius would be a few cm. Although it would exert a force of 1 g if you were one Earth radius away (6000 km) but if we manage to make an Earth-weight black hole it will be a triumph of miniaturization. We will have succeeded in finally making a black hole small enough to fit in your pocket.

It just puts into perspective that there needs to be a risk benefit standard. Now if they said there was a one in a million chance of making a black hole the size of a basketball then I'd be saying it wasn't worth the risk.

As a reasonably modern person you would expect to benefit from advances made by research into physics. That is why the risk might be acceptable to you. Somebody who has a different lifestyle might have a different perspective on this.

there's that chance says that there is zero chance of it lasting more than a few milliseconds.

Nobody really knows what happens to microscopic black holes. There is no experimental evidence.

The collider is so cool you could keep a side of meat in it for a month. It is so incredibly hip it has trouble seeing over its own pelvis. Hey, you sass that hoopy large hadron collider, there's a frood that really knows where its towel's at.

Have you seen the cost of this large hagrid colliding thing? What is the point of wasting all that tax money looking for that higgs boson that, when found, will probably have been stepped on or at least be all dirty. Wouldn't it make more sense just to write the boson off at the next inventory count and just requisition a NEW higgs boson from stores?Okay, we need to be more environmentally aware now, and less wasteful of materials but this just confirms what people have told me about these CERN guys; they just take stuff to extremes.

light does not stop accelerating at 186,000 mps, it travels at 186,000 mps (well... approximately) in a vacuum. it does not accelerate, it travels at a constant speed (as far as we know), so c is a constant. Now it does slow down as it travels through a medium (water, air, crystal), but mostly that is caused by the absorption and re-emmitance (is that a word?) of the photons.

Depends on your point of view. The *apparent* speed of light (group velocity - that is, the speed of wave propagation) in a medium is variable, but individual photons have zero mass, thus *can not* experience acceleration. In terms of basic classical physics, a=F/m, m is 0 - division by zero, the equation is unsolvable, i.e. the concept simply does not apply.

The apparent movement of galaxies moving away from each other is what gives rise to the notion of the big bang. What if this is just an optical illusion? If matter in the universe is gradually shrinking in size (there is plenty of room for a lot of shrinkage in each atom) by a means we are not yet familiar with (forty standard kilogram weights around the world are mysteriously different weights now), then the universe started off in a superheated cloud and gradually cooled off in our local area. As galaxies

Luxury. Well when I were a lad, our dad used to make 160 of us live in a shoebox in the middle of deep space. Millikelvins?? We *dreamed* of millikelvins....

Paradise. Why, when I was growin' up, we were all huddled together inside a higgs boson in the middle of a black hole. Every morning, we'd lick the black hole clean with our tongues, then huddle around the event horizon rubbing our hands together until it went *above* absolute zero.

Because its not being built by Americans. It's being built by European Organization for Nuclear Research, A.K.A. 'CERN [wikipedia.org]' (Conseil Europeen pour la Recherche Nucleaire). Thats why its not in the USA, and why its in France.

Thought not - and seeing as how it was bits falling of a US plane that caused the disaster that killed off Concorde, you've got nothing to shout about.

Concorde was an elementally flawed idea - too small and too expensive to develop and run, but I saw the A380 at Farnborough the other day, and that's going to kill Boeing in the next few years, especially if they lose the USAF tanker contract too.

And 'super-massive supercollider'?

That's just a drag strip with 2 SUVs loaded with lard-arsed Yanks playing chicken:o)

Indeed, getting 1.9K in a lab, or in a single NMR magnet is not a big deal.
Try to do it with 1232 huge magnets, spread around 26.6 km, being some 100m underground,
and using 7600 km of super-conducting "cable" (270 000 km of superconducting "strand"). This is roughly 4700 tons of material to keep at 1.9K, and 120 tons of helium being recirculated all the time through these stuff to assure 150 kW of HEAT power is dissipated.
Noone ever has done a similar cryogenic installation at such scale before!

I agree, it's the scale of the cooldown that's impressive. In fact, when the LHC is running at full power, it will be drawing more power than the entire city of Geneva, and most of that power will go towards cooling.

I agree, the scale is something impressive. And certainly the scaling issues could make for an interesting and informative article. Or maybe not. Maybe it's one of the easiest of the many challenges they faced when building this thing (This is the cue for any slashdotters working on the project to chime in and educate us). The article certainly has little to say about the engineering challenges. But look at the headline and lede of the article:

A vast physics experiment built in a tunnel below the French-Swiss border is fast becoming one of the coolest places in the Universe.

Now tell me, what do you think a reader without any scientific knowledge will take away from this article, that the scale of the cooling is what makes it challenging, or the temperature itself? That 1.9 K is an exotically low temperature for physics experiments, or that it's mundane? This is what bothers me about most science journalism. The misleading statements and lack of information.

Come to think of it, that's the problem with most non-science journalism too.

I respectfully have to disagree with you. Given the *scale* of the engineering at the LHC. Lord knows what safety procedures you need (quench
anyone?). It's not the temperature that's the thing, it's maintaining the whole darned thing at that temperature... Engineering is *always* in the
details, and oh my god the LHC has most of those maxed out to an extent that makes my brain hurt.
You can only get blase about this if you think
E.E.Doc Smith's space operas are dull..

From Wikipedia: "it is possible that some molecules reach a state of no kinetic energy while others have more kinetic energy than the measured energy. Since the average between the lower and higher measurements give us the temperature we read, it is quite possible for some molecules to reach zero Kelvin."

Yes, it is possible for things to be colder, like in the above extreme example of molecules with no kinetic energy. I think the novel part of the Large Hadron Collider is its scale. Bringing something this

Weeell, it is the biggest cryogenic installation ever, the most complex machine ever built, the largest and most powerful particle accelerator ever, and they're pushing lots of data handling limits, such as network transfer speed, storage space and CPU cycles used. Now, what did I forget?

Bullshit. 1.9K to cool the magnets (even "high" temperature superconductors have a critical temperature of up to 138K (current record)) which keep your particles on track so that they can produce really high temperatures when colliding inside one of the particle [wikipedia.org] detectors [wikipedia.org].

I didn't mod the comment "Troll", and I don't consider it so. You cannot moderate and comment in the same thread - when you comment, your mods are cancelled.

As for burying it, how else in Europe are you going to build something 27 km across and dead level, with mounting points for thousands of tons of equipment? It is not below a mountain, it is below farmland. Anywhere reasonably flat in Europe is covered with towns and villages and criss-crossed with roads. And the flatness requirement is *exact*, so if the ground is only fairly flat, you will have to have bits in tunnels and/or on stilts anyway. On stilts is bad for carrying heavy loads. And you don't want your hypersensitive particle detectors triggered by cosmic radiation, so they will have to be heavily shielded anyway. Since the equipment needs to be well protected from accidents and weather for purely engineering reasons (big magnets, huge currents, super-cooling, vacuum). I could see problems with those magnets distorting every CRT-based television for hundreds of yards. The reason for burying it is purely for experimental purposes rather than safety. It is re-using the tunnel dug for an earlier detector, decommissioned a few years ago.